Temperature stability, transition metal

A couple of theoretical studies [5,19] have hitherto attempted to estimate the Peierls transition temperature (Tp) for metallic CNT. A detailed theoretical check with respect to the stability of metallic wavefunction in tube (5, 5) has also... 

The temperature regimes for the stability of intermediates is different for various transition metals. For example on Fe(lll) the adsorbed ethylene decomposes partially at 200 K, while the conversion to surface carbon is complete at 370 K. Similarly, on nickel faces molecular chemisorption of ethylene is restricted to temperatures below ambient. At temperatures between approximately 290 K and 450 K ethylene chemisorption on nickel... 

In the practical application, the chemical stability of these polymers at high temperature will essentially depend on the content of oxygen and ions of transition metals in the brine. It is the reason why we have investigated their behaviors for several months ( at least 3), at 80°C and under three main conditions (see fig.3). 

More than 3000 different enzymes have been extracted from animals, plants and microorganisms. Traditionally, they have been used in impure form since purification is expensive and pure enzymes may be difficult to store and use. There is usually an optimum temperature and pH for maximum activity of an enzyme. Outside these optimum conditions, activity may simply be held in check or the enzyme may become denatured , i.e. altered in such a way that activity is lost permanently, although some forms of denaturing are reversible. Many enzymes are also sensitive to transition-metal ions, the effect being specific to particular metal ions and enzymes. In some cases, certain metal ions are essential for the stability and/or activity of an enzyme. In other cases, metal ions may inhibit the activity of an enzyme. Similarly, certain organic compounds can act as enzyme inhibitors or activators. 

Syntheses of aryl organometallics other than polyhalogenoaryls by thermal decarboxylation are comparatively rare. There are several reasons for this. For transition elements, the thermal stability of simple aryls is often low, especially by comparison with polyhalogenoaryl derivatives, thereby excluding syntheses at elevated temperatures. Electron-withdrawing substituents frequently aid thermal decarboxylation (Section III,A-D), and their absence inhibits major mechanistic paths to both transition metal and main group element derivatives, e.g., SEi (carbanionic) and oxidative addition (Section II). In thermal decomposition of... 

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